1. Field of the Invention
The present invention relates generally to an apparatus and a method for inserting discrete articles into surgical cartridges, and more particularly relates to an improved device and method for inserting staple drivers into surgical stapling cartridges.
2. Description of the Related Art
In the field of microsurgery, a surgical instrument having a cutting blade traverses a specific path through tissue. One feature of the surgical instrument is a single-use cartridge that is a holder for surgical staples. The cartridge is an elongated plastic body with a longitudinal channel that serves as a guide for a surgical blade. The cartridge has rows of small staples on opposite sides of the channel, and these rows are aligned parallel to the guide channel. Drivers are inserted in apertures (also called “pockets”) aligned with the rows in order to push the staples out of the cartridge and through the adjacent tissue. Before the blade has made its cut, each side of the incision is stapled together by displacing the drivers relative to the cartridge. This displacement forces the staples against an anvil on the opposing side of the surgical instrument as the cartridge and the anvil deflects the points of the staples into a clasping position.
There may be as many as fifty or more very small staples on each side of a two inch incision. Each staple can be driven simultaneously into the tissue to close the incision by the correspondingly small drivers. The task of inserting the drivers into the cartridge is labor-intensive due to the small size of the drivers.
One prior art system for holding the very small staple drivers before and during mounting in the cartridge pockets includes a plastic holder that is referred to as a “tree.” There are multiple aligned “branches” on the tree, and a driver is mounted to the end of each branch, such as integrally molding the driver to the branch. During installation of the drivers, the cartridge is placed in a holding apparatus, and the tree is hand-manipulated to place a driver at the entrance to each pocket, or at least at the entrance to as many pockets as there are drivers on the tree. This is normally accomplished by inserting each driver into a funnel-shaped passage that is aligned with a pocket. Each driver is subsequently separated from its respective branch and driven into the associated pocket of the cartridge. The separation of the drivers from the branches of the tree is accomplished by flexing the branches of the tree manually to fracture the joint between the driver and the branch. Then, a hand-manipulated tool is used to press each driver down into the cartridge pocket to near the pocket opening on the opposite side of the cartridge as the pocket entrance.
The operation of manually aligning each driver with a pocket, flexing the branches and pressing from the hand-operated tool can misalign the drivers relative to the axes of the respective pockets. The drivers are inserted into the funnel-shaped passages on the fixture so as to align each individual driver with an associated pocket on the cartridge. However, the funnel-shaped passages do not fully cure the misalignment problem, because the funnels do not fully engage the driver to be inserted.
If the driver is not properly aligned within the pocket, the staple which is ejected by displacement of the staple driver may be inaccurately bent during the surgery. In addition, the misalignment of the staple driver in the pocket can increase the force needed to eject a staple or prevent the ejection of that staple entirely.
An additional potential problem arises due to slight variations in the sizes of the pockets and the drivers due to the minute structure involved and the fact that both the cartridge and the staple drivers are formed of thermoplastic resin, which cools from a liquid or semi-liquid with imperfect and irregular shrinkage. This combination of factors can create gaps between the components, which can exacerbate alignment problems. Additionally, inversion of the cartridge after assembly can result in some of the drivers falling out of their pockets. If a staple driver is absent, no staple will be driven into the tissue at that point in the incision, which increases the chances of surgical complications.
Yet another problem is the imprecision in the process of separating the staple drivers from the branches of the plastic “tree”, a process referred to as “degating.” The drivers are mounted to the tree prior to their insertion in the pockets, and must be removed from the tree before or during the insertion process. The separation of a driver from the tree is not precise, and therefore it leaves a remnant of material on one side of each driver. The remnants of material left on the drivers are not a predictable size, and often the remnants are larger than desired. While it is not practical to remove all of the “branch” material from the side of each driver in the separation process, it is important that the amount of material left on each driver be relatively consistent between drivers. This is because the material left on the side tends to cause friction when the staple driver is used in surgery. If the amount of material left is consistent, it allows a user of the staple cartridge to accurately predict the amount of force needed to expel the staples during surgery. In addition, the smaller the volume of material left, the less friction will be generated, and the less the force required to use the staple cartridge.
It is known in the prior art to insert drivers mechanically into surgical stapling cartridges, as shown in U.S. Pat. No. 5,836,147 to Schnipke, U.S. Pat. No. 5,653,928 to Schnipke, and U.S. Pat. No. 6,158,205 to Schnipke et al., all of which are incorporated herein by reference. These patents show machines that require people to position the cartridges and the holders that contain the drivers relative to the machine, and then actuate the machine to insert the tiny drivers into the pockets in the cartridges. After a fraction of the total number of drivers is inserted by one machine, the cartridge is then manually transported to the next machine, which inserts another fraction of the drivers.
If a driver is improperly inserted into a cartridge, or is omitted, the cartridge is either discarded or repaired. Thus, errors in insertion of the tiny parts can result in wasted time and/or product.
Even the machines disclosed and claimed in the patents referenced above, although representing a significant improvement over the prior art, have problems, especially with the pockets collapsing slightly during cooling. These collapsed pockets either prevent drivers from being driven into them or damage the drivers that are driven into them as a result of scraping.
In U.S. Pat. No. 6,729,119 to Schnipke et al., which is incorporated herein by reference, a robotic loader is discussed for use in filling the cartridges discussed herein. However, this patent does not address the problems that continue to exist on the non-robotic devices discussed above.
Therefore, there is a need for an improved machine for loading drivers into surgical cartridges.